A considerable effort has been expended in the steel container industry to reduce the cost of materials employed in the manufacture of steel drums used principally for the shipping and storage of industrial products. Any reduction in the container wall thickness is, of course, viewed as a substantial saving. There are certain areas of the drum construction, however, where the wall strength becomes quite critical. One such area of criticality is that section of the container wall immediately surrounding the drum closure which is permanently inserted within the drum wall.
This closure, in many instances, consists of a steel bushing or flange having an internally threaded cylindrical neck with a resilient sealing gasket therearound and having a laterally extending polygonal base surrounding its lowermost end. A perforated container wall section overlies the flange neck and base with the upper unthreaded portion of the flange neck beaded outwardly over the surrounding drum stock so as to permanently secure the flange in place. The closure is completed with the threaded engagement of a closure plug and application of an overlying tamper-resisting drum seal. It can be readily appreciated that as the rigidity of the drum stock immediately surrounding the closure flange is diminished, all things being equal, a consequent reduction in resistance to turning torque between the flange and drum stock results. As high torque resistance for proper seating and unseating of the closure plug is essential to good closure performance, various attempts have been made to improve the torque characteristic on flange insertions in light gage drums. Heretofore, these attempts, in large part, have been directed toward the provision of suitable reinforcing collars designed to overlie the drum stock section immediately surrounding the flange in order to achieve the necessary strength. This approach, though functionally adequate, introduces an additional undesirable cost factor.
The instant invention, as hereinafter disclosed, seeks to achieve the necessary degree of torque resistance in the closure container wall joint without resort to additional reinforcing parts and their attendant costs. This has been accomplished by forming the drum stock so as to surround and closely overlie the flange neck and base and also extend well below the outer exposed edge of the flange base. This drum stock formation causes the periphery of the flange base to be completely embedded in the drum stock embossment so that only after severe distortion of the embossment can relative rotational movement between the flange and container wall take place. This specific formation of the drum stock about the flange base, coupled with other features of the invention to be described hereinafter, has given rise to a distinct improvement in the drum closure field and particularly in improving the torque-resistance characteristic of flange insertions in light gage drums.
It is, accordingly, a primary object of the invention to provide a new and improved threaded closure construction for light gage steel drums.
Another object is to provide a new and improved flange insertion in light gage drums having superior torque resistance characteristics.
Another object is to provide a closure for light gage drums wherein the sealing efficiency of the flange gasket is protected against the deleterious effect of elevated temperatures commonly encountered in the curing of drum coatings.
A further object is to provide a drum closure construction including an overlying drum seal having improved tamper-resisting effectiveness.
Other and more detailed objects will in part be obvious and in part pointed out as the description of the invention taken in conjunction with the accompanying drawing proceeds.